Field
Exemplary embodiments of the present invention relate to a light emitting module, and more particularly, to a lens for surface illumination and a light emitting module for surface illumination having the same.
Discussion of the Background
In general, a light emitting module for backlighting a liquid crystal display or a light emitting module for surface illumination, which is used in a surface illumination apparatus, includes a light emitting device mounted on a circuit board, and a lens for distributing light emitted from the light limiting device at a wide angle. By uniformly distributing the light emitted from the light emitting device using the lens, it is possible to uniformly irradiate a wide area with a small number of light emitting devices.
FIGS. 1A and 1B are respectively sectional and perspective views schematically illustrating a conventional light emitting module and a conventional lens.
Referring to FIGS. 1A and 1B, the light emitting module includes a circuit board 100, a light emitting device 200 and a lens 300. The circuit board 100 is a printed circuit board on which a circuit for supplying electric power to the light emitting device 200 is formed.
The light emitting device 200 generally includes a light emitting diode (LED) chip 210, a molding portion 230 covering the LED chip 210, and a package substrate 250. The molding portion 230 may include a phosphor used for converting the wavelength of light emitted from the LED chip 210 and have a lenticular shape. The package substrate 250 may have a recess for mounting the LED chip 210 therein. The light emitting device 200 is electrically connected to the circuit board 100.
Meanwhile, the lens 300 includes a lower surface 310 and an upper surface 350, and may also include a flange 370 and leg portions 390. The leg portions 390 are attached onto the circuit board 100, so that the lens 300 is disposed above the light emitting device 200. As shown in FIG. 1B, the leg portions 390 are usually comprised of three leg portions that are disposed at apexes of a regular triangle.
The lens 300 has an incidence surface 330 on which light from the light emitting device 200 is incident, and an exit surface 350 from which the light exits. The incidence surface 330 is an inner surface of a shell-shaped concave portion 320 formed on the lower surface 310 of the lens 300. Since the concave portion 320 is disposed above the light emitting device 200, light emitted from the light emitting device 200 is incident into the lens 300 through the incidence surface 330. The exit surface 350 allows the light incident into the lens 300 to exit over a wide viewing angle.
In the conventional light emitting module, the light emitted from the light emitting device 200 is distributed through the lens 300, so that uniform light can be achieved over a wider area. However, since the light emitting device 200 mounted on the circuit board 100 employs the package substrate 250, the size of the light emitting device 200 is relatively large. Accordingly, the entrance and height of the concave portion 320 for forming the incidence surface 330 of the lens 300 are also relatively larger, and as a result, it is difficult to slim the lens 300. Further, since the viewing angle of the light emitted from the light emitting device 200 is relatively narrow, there is a limitation on distribution of light through the lens 300.
Furthermore, since the light emitting device 200 is positioned beneath the lower surface 310 of the lens 300, a portion of the light emitted from the light emitting device 200 is not incident into the lens 300 but is likely to be lost beneath the lower surface 310 of the lens 300.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form any part of the prior art nor what the prior art may suggest to a person of ordinary skill in the art.